It doesn't matter if i have the ports open on my router at home, it doesn't work with other players unless I play through Hamachi. (or am plugged directly to the modem)
Definitely not a firewall issue on your PC? (Could check by temporarily disabling when someone else is trying to get in).
If not, have you tried setting up port forwarding on your router? I.e. set up a rule to forward traffic that's received on port 2057, to your PC's IP address on the internal network. Should be a standard option on most home routers (e.g. on Linksys routers it is under 'port forwarding and advanced gaming' options or somesuch)...
(Oh yeah... OCC

)